Splash-lubrication engines are generally known and widely used in small engines, such as those used in lawn mowers, outboard marine operation, lawn equipment, generators, power washers, snow blowers, and so on. In a splash lubrication engine, oil that gathers in the lower part of the crankcase, such as in the oil pan, oil tray, or other reservoir, is thrown upward as droplets (or fine mist) to provide lubrication to various parts of the engine, such as valve mechanisms, piston pins, cylinder walls, and piston rings. In one such typical splash-lubrication engine design, dippers on the connecting-rod bearing caps enter the oil trough located in the lower part of the crankcase and with each crankshaft revolution produces the oil splash. A passage may be drilled in each connecting rod from the dipper to the bearing to ensure lubrication. In certain instances, splash-lubrication ermines may be lubricated through a combination of splash lubrication and force feeding. In certain such embodiment, an oil pump may keep the oil trough full so that the engine bearings can always splash enough oil onto the other parts of the engine.
Furthermore, gears in enclosed gear drives may also be splash lubricated. In this case, it is the tooth of the gear that is dipped in oil, which is then spread onto the teeth of the meshing gear as it turns.
Many splash-lubrication engines do not have an oil treatment system. As used herein, oil treatment includes oil filtration and/or replenishing oil with desired additives. Engine oil degrades because of accumulation of wear particles, fuel, moisture, and sludge. Also, oil additives are consumed—detergents, dispersants, corrosion inhibiters, and friction reducers. On splash lubricated engines, oil degradation is controlled by user maintenance—drain out the old oil, refill with new oil. Thus, oil treatment in splash-lubrication engines is desirable fur obvious reasons. However, it has been generally thought that adding an oil treatment system to a splash-lubrication engine would require significant redesign of many castings, thereby resulting in a significant expenditure.
Additionally, new ways of treating oil in internal combustion engines having forced oil flow circulation is desired.